Size: 3475 km (2172 miles) in diameter
Temperature: at night -153 degrees Celsius (-218 degrees Fahrenheit) ;
daytime, 107 degrees Celsius (250 degrees Fahrenheit)
Atmosphere: almost none
Average distance from Earth: 384,400 km (240,250 miles)
Time taken to orbit Earth: 27.322 days
Time taken to rotate once: 27.322 days
Average time from new moon to new moon: about 29.5 days

1. The Moon is rocky.

It isn't hot like the Sun. The Moon shines because it reflects sunlight. We can see planets because they also reflect sunlight. If you were on the Moon, you could see the Earth shine.

2. The Moon orbits the Earth.

The Sun always lights half of the Moon. We see different parts of the sunlit half as the Moon goes around Earth. This is why the Moon seems to change shape. These changes are called "the phases of the Moon," and the Moon takes 29.5 days to go through them all and back to the start.

3. The Moon turns around as it goes around the Earth.

The Moon turns once on its axis during each orbit, so we always see the same side of the Moon. People used to call the far side of the Moon the "dark side." That side gets its share of sunlight, but we can't see it from Earth. Moon probes and twenty-seven Apollo astronauts have seen the far side of the Moon.

4. The Moon is about 4.6 billion years old.

The Earth is also about 4.6 billion years old. The early Solar System had lots of big rocks and small planets crashing around. Most astronomers think the Moon was made when a large asteroid hit the Earth and vaporized a big chunk of it.

5. There is no air on the Moon.

You couldn't breathe and it would also be silent. We can talk to each other on Earth because sound waves go through the air. The Apollo astronauts on the Moon spoke to each other using radio. Radio waves are like light waves - they can go through empty space.

6. There is no liquid water on the Moon.

There is some water on the Moon, but don't imagine swimming in it. The water is frozen and the Moon is drier than Earth's deserts.

7. There is no weather on the Moon.

This means the surface of the Moon is very old. On Earth wind and rain and moving water wear away the rocks. Rocks are regularly recycled. Neil Armstrong's famous footprint is probably still on the Moon after more than forty years. It wouldn't last long on Earth.

8. The Moon has light and dark patches.

Some people think they make a face ("the man in the moon"), others say a rabbit. The dark patches are areas of dark rock. Long ago large asteroids hit the Moon and made big shallow craters. Later lava filled them and hardened into a dark rock. The light-colored rocks of the highlands surround them.

9. The force of gravity is weaker on the Moon than on the Earth.

This is because the Moon is smaller than the Earth and is less dense. (Density is how much matter there is in a cube of a given size.) If you weigh 80 lbs (36 kg) on Earth, on the Moon you would only weigh about 13 lbs (6 kg). You could have a good time playing games there.

10. The Moon is the only heavenly body on which humans have landed.

Most astronauts don't go very far into space, but twelve Apollo astronauts have walked on the Moon. The first man on the Moon, Neil Armstrong, died on August 25, 2012.